1. Field of the Invention
The present invention relates to a conveying system and particularly, pertains to a conveying system utilizing a linear pulse motor.
2. Description of the Prior Art
Of late, to meet the demand for improvement in stopping accuracy at stations in conveying works, which has arisen in accompaniment with automation in working and assembling in mechanical industries, conveying systems utilizing linear pulse motors are in use, taking the place of such conveying means as belt conveyors, etc.
FIG. 1 is a diagram for explanation of the main part of a conveying system utilizing a linear pulse motor which has heretofore been in use.
Referring to this diagram, 3 denotes a base; 31, tracks provided at both ends of the aforementioned base; 2, a conveying truck; and 24, wheels placed on both sides of the aforementioned conveying truck.
Thus 1 designates stators fixed at the top of the aforementioned base 3; an iron core 11 composes the aforementioned stator, together with a coil 13; and 21 designates a mover formed integral with the conveying truck 2 at the bottom center thereof, which composes a linear pulse motor, together with the aforementioned stators 1.
Numeral 25 denotes guide rollers for preventing rolling of the conveying truck while rolling on both inside surfaces of the aforementioned tracks 31. These guide rollers 25 are located at the bottom of the conveying truck 2.
The magnetic flux produced by the aforementioned stator 1 is directed at nearly a right angle to the forwarding direction of the conveying truck 2.
As shown in this diagram, the stator 1 is placed nearly at the center of the base 3 or just in the intermediate position between the two tracks 31.
Conveying systems utilizing the linear pulse motors of such a construction have the following disadvantages:
1 Since the stator 1 is located at the central part between the tracks 31 and the mover 21 is placed at the central part of the conveying truck 2 in correspondence thereto, the bottom part of said conveying truck 2 is closed, leaving no room for providing any openings.
This makes it impossible to subject the work carried on the conveying truck 2 to any operation performed from below, resulting in inconvenience in assembling work, etc., of vehicles or home electric appliances.
2 With the mover 21 located at the center of the conveying truck 2, the electromagnetic attraction between the stator and the mover 21 can not be ignored.
Besides, on account of the fixed position of the mover 21 and its weight, the bending moment at the central part of the conveying truck 2 becomes very large. Consequently, due to the aforementioned two causes, the conveying truck 2 as a whole is deformed in a bow shape, making it difficult to hold the clearance between the mover 21 and the stator 1 at a specified value. As a result, the operation of the linear pulse motor becomes unstable, causing various ill effects on the conveying state.
3 Besides, with the mover 21 integrally composed with the conveying truck 2, the conveying truck 2 as a whole has a large weight, resulting in a disadvantage of large power requirement.